Simplify the following expression: $y = \dfrac{9}{5k} + \dfrac{7}{8k}$
Explanation: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5k$ and $8k$ $\lcm(5k, 8k) = 40k$ $ y = \dfrac{8}{8} \cdot \dfrac{9}{5k} + \dfrac{5}{5} \cdot \dfrac{7}{8k} $ $y = \dfrac{72}{40k} + \dfrac{35}{40k}$ $y = \dfrac{72 +35}{40k}$ $y = \dfrac{107}{40k}$